Intra-Scan Variability of Natural Shear Wave Measurements

Shear wave elastography can potentially be used to diagnose an increased stiffness of the myocardium for patients with diastolic heart failure. This study focusses on the shear waves induced by aortic valve closure in the interventricular septum. The propagation speed of these shear waves is expected to be related to the stiffness of the myocardium and is determined along a manually-drawn M-line over the myocardium. In this study the effect of M-line location and angle is systematically investigated. In-vitro, measurements were performed using a PV A slab phantom, and in-vivo using three pigs with open chest. We found large global differences in propagation speed for different M-line locations over the interventricular septum, possibly having physiological causes. To avoid these physiological effects, we averaged the propagation speed of 10M-lines manually drawn at the endocardial side of the interventricular septum. A local median of intra-scan interquartile range of about 0.6 m/s was found.